The present invention relates to scroll type machines. More particularly, the present invention relates to hermetic scroll compressors incorporating a vapor injection system which utilizes a heat exchanger or a flash tank which is mounted directly to the shell of the scroll compressor.
Refrigeration and air conditioning systems typically include a compressor, a condenser, an expansion valve or equivalent and an evaporator. These components are coupled in sequence in a continuous serial flow path. A working fluid or refrigerant flows through the system and alternates between a liquid phase and a vapor or gaseous phase.
A variety of compressor types have been used in refrigeration and air conditioning systems, including but not limited to reciprocating compressors, screw compressors and rotary compressors. Rotary compressors can include both the vane type compressors as well as the scroll machines. Scroll machines are constructed using two scroll members with each scroll member having an end plate and a spiral wrap extending generally perpendicular to the respective end wrap. The spiral wraps are arranged in an opposing manner with the two spiral wraps being interleaved or interfitted with each other. The scroll members are mounted so that they may engage in relative orbiting motion with respect to each other. During this orbiting movement, the spiral wraps define a successive series of enclosed pockets or spaces, each of which progressively decreases in size as it moves inwardly from a radially outer position at a relatively low suction pressure to a central position at a relatively higher or discharge pressure. The compressed fluid exits from the enclosed space at the central position through a discharge passage formed through the end plate of one of the scroll members.
Refrigeration and air conditioning systems are now incorporating vapor injection systems where a portion of the refrigerant in gaseous form is injected into the enclosed pockets or spaces at a pressure which is intermediate the low suction pressure and the relatively high discharge pressure. This gaseous refrigerant is injected into the enclosed pockets or spaces through one or more injection ports which extend through one of the two scroll members. The injection of this gaseous refrigerant has the effect of increasing both the refrigeration or air conditioning system""s capacity and the efficiency of the refrigeration or air conditioning system. In refrigeration or air conditioning systems where vapor injection is incorporated to achieve maximum capacity and maximum efficiency increases, the development engineer attempts to provide an injection system which will maximize the amount of refrigerant gas that is injected into the enclosed pocket as well as maximizing the intermediate pressure at which the refrigerant gas is injected into the enclosed pocket. By maximizing both the amount of refrigerant gas as well as the pressure of the refrigerant gas that is injected, the system capacity and the system efficiency of the refrigeration or air conditioning system are maximized.
When developing the vapor injection system, the development engineer must consider the source for the vapor that is injected into the pockets. Typically, the vapor refrigerant source is through a connection at a position within the refrigeration circuit and a device such as a flash tank or an economizer is utilized to separate vapor refrigerant from gaseous refrigerant to ensure that only gaseous or vapor refrigerant is injected into the enclosed pockets or spaces. When accessing liquid refrigerant from a position within the refrigeration circuit, the vapor or gaseous refrigerant is typically piped to the compressor through a fluid line which extends between the position within the refrigeration circuit and the compressor. The use of fluid piping between the source of vapor or gaseous refrigerant and the compressor provides a system where pressure drop of the gaseous refrigerant can occur due to fluid line losses and/or temperature loses. While it is possible to insulate this line in order to limit temperature losses, this insulation adds additional cost and complexity to the refrigerant or air-conditioning system as well as presenting problems during the servicing of the system.
Thus, the continued development of vapor injection systems is directed towards increasing the amount and pressure of intermediate pressurized vapor that can be injected into the enclosed spaces.
The present invention provides the art with a vapor injection system where a flash tank, an economizer or a heat exchanger is mounted directly to the hermetic shell of the compressor. The direct attachment of the flash tank, the economizer or the heat exchanger eliminates all external tubing required for the intermediate pressurized gaseous refrigerant. The direct attachment of the flash tank, the economizer or the heat exchanger provides the advantages of a more compact single unit, there is less pressure drop, the installation is easier, it is not necessary to isolate or insulate the vapor injection fluid line, there are fewer components that need to be connected during installation and the refrigeration or air conditioning system will be lower in cost.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.